Cancer effects virtually every part of the human anatomy. Each area of cancerization is unique and requires unique treatment. The present invention involves treatment of cancer localized in the oral cavity. Because of the difficulty in determining the extent of premalignant and malignant change, cancerization of the oral cavity is extremely difficult to manage. Current methods of treating this problem include excision, cryosurgery, CO.sub.2 laser ablation, and selective destruction of premalignant as well as early malignant tumors by photodynamic therapy.
Any type of selective excision of condemned mucosa of the oral cavity presents inherent difficulties. It is extremely difficult to clinically differentiate malignant, premalignant, and benign mucosa because frequently the entire oral cavity mucosa appear to be condemned.
Photodynamic therapy, PDT, has been used in various treatments of cancers. Photodynamic therapy is a relatively new therapeutic modality which uses a photosensitizing drug such as hematoporphyrin derivative (HPD) or its purified form dihematoporphyrin ether (DHE) which selectively localizes in tumors and on activation by exposure to light results in cell necrosis.
The first described use of such a photosensitizer in a biological system occurred at the turn of the century when the lethal affect of acridine dye on paramecium incubated and exposed to light was reported. Numerous other substances have subsequently been used as photosensitizers, for example tetracycline, berberine sulphate, acridine orange, fluoresceine as well as various porphyrins. Porphyrins are particularly preferred since they are selectively taken up by tumor cells.
HPD and DHE appear to fill most of the criteria for a satisfactory photosensitizer for use in diagnosis and treatment of malignant diseases in humans. The treatment using HPD and DHE is disclosed for example in Clark U.S. Pat. No. 4,336,809 and U.K Patent Application No. 2,125,986. The methods disclosed in these references suffer from the same disadvantage of the prior methods of treatment of cancer of the oral cavity in that they are used to destroy or remove specific tissue. This requires identification and selection of the diseased tissue which is difficult if not impossible.